The `instantiate` method in `Environment` has been refactored to return
`Result<Rc<Closure>, String>` instead of `Rc<NativeFunction>`. This
change separates the creation of a `Closure` from its execution,
allowing the caller to manage the `VM` lifecycle and choose the
appropriate execution strategy (e.g., single run vs. repeated benchmark
iterations).
The `NativeFunction` type is now exclusively used for true Rust
intrinsics. The benchmark runner has also been updated to reuse a single
`VM` across iterations, improving performance by avoiding repeated VM
allocations.
Brummel
b6dcdbde8d